docs: def get_fields(config):
      """
      Recursive generator that yields the field names in the config file
  
      :param config: The configuration file that contains the specification of the extractor
      :return: The field names in the config file, through a generator
  
      """
      for data in config['scraping']['data']:
          if data['field'] != '': 
              yield data['field']
      if 'next' in config['scraping']:
          for n in config['scraping']['next']:
              for f in get_fields(n): 
                  yield f